EPUB 3.1 Changes from EPUB 3.0.1

Editor's Draft 30 January 2016

This document summarizes changes included in the most current draft of EPUB 3.1. Note that this list of changes is not exhaustive; additional changes are under consideration and will be included in forthcoming drafts.

Important Note about Changes

The EPUB working group has opted for a radical change approach to the addition and deletion of features in the 3.1 revision to move the standard aggressively forward with the overarching goals of alignment with the Open Web Platform and simplification of the core specifications.

It is expected that some of these radical changes will provoke strong reactions both for and against, as the working group has taken this approach to fully gauge the community response.

The changes made in these drafts are not final until the revision concludes, and if strong negative reactions are voiced from the community they will be reviewed for future drafts.

Links to the relevant open issues in the working group tracker have been included for each change listed in this document. To express concerns about any of these changes, please add a comment to the appropriate issue.

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http://www.idpf.org/epub/31/spec/epub-changes-20160130.html
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Editors

Markus Gylling, International Digital Publishing Forum (IDPF)

Matt Garrish, Invited Expert

Copyright © 2010-2016 International Digital Publishing Forum™

All rights reserved. This work is protected under Title 17 of the United States Code. Reproduction and dissemination of this work with changes is prohibited except with the written permission of the International Digital Publishing Forum (IDPF).

EPUB is a registered trademark of the International Digital Publishing Forum.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document.

This document is a draft produced by the EPUB Working Group under the EPUB Working Group Charter approved on 8 July 2015.

This document is not considered stable and may be updated, replaced or obsoleted at any time. Its publication as a draft does not imply endorsement by IDPF membership or the IDPF Board. The document should only be cited as a work in progress.

Feedback on this document can be provided to the EPUB Working Group's mailing list or issue tracker.

This document is governed by the IDPF Policies and Procedures.

  1 Introduction

EPUB® is an interchange and delivery format for digital publications, based on XML and Web Standards. An EPUB Publication can be thought of as a reliable packaging of Web content that represents a digital book, magazine, or other type of publication, and that can be distributed for online and offline consumption.

This document, EPUB 3.1 Changes from EPUB 3.0.1, describes changes made in the first major revision of the EPUB 3.0 specifications, highlighting key changes and additions.

This document is non-normative. Consult the EPUB specifications for definitive information on EPUB 3.

Unless otherwise specified, terms used herein have the meaning defined in Terminology [EPUB31].

  1.1 EPUB Revision History

EPUB had its roots in the interchange format known as the Open EBook Publication Structure (OEBPS). OEBPS 1.0 was approved in 1999 by the Open eBook Forum, an organization that later became the International Digital Publishing Forum (IDPF). Subsequent revisions 1.1 and 1.2 were approved by the IDPF in 2001 and 2002 respectively.

It was realized that a need existed for a format standard that could be used for delivery as well as interchange, and work began in late 2005 on a single-file container format for OEPBS, which was approved by the IDPF as the OEBPS Container Format (OCF) in 2006. Work on a 2.0 revision of OEBPS began in parallel which was approved as the renamed EPUB 2.0 in October, 2007, consisting of a triumvirate of specifications: Open Package Format (OPF), Open Publication Format (OPF) together with OCF. EPUB 2.0.1, a maintenance update to the 2.0 specification set primarily intended clarify and correct errata in the specifications, was approved in September, 2010. [OPF2] [OPS2] [OCF2]

Work on a major new 3.0 revision of the EPUB specifications began in 2010, with the goal of aligning EPUB more closely with HTML5, and in the process bringing new, native multimedia features, sophisticated CSS layout rendering and font embedding, scripted interactivity, enhanced global language support, and improved accessibility. A new specification, EPUB Media Overlays was also introduced, enabling text and audio synchronization in EPUB Publications. To better align the specification names with the standard, the Open Package Format specification was renamed EPUB Publications and the Open Publication Format specification was renamed EPUB Content Documents. The EPUB 3.0 specifications were approved in October, 2011. [Publications30] [ContentDocs30] [OCF30] [MediaOverlays30]

The EPUB 3.0.1 revision was undertaken in 2013-14. Although introducing mostly minor fixes and updates, it did see the integration of Fixed Layout Documents, which give Authors greater control over presentation when a reflowable EPUB is not suitable for the content. [Publications301] [ContentDocs301] [OCF301] [MediaOverlays301]

  2 Specification Reorganization

To simplify reading and referencing of the EPUB standard, a major reorganization of the specifications was undertaken in this revision. Foremost among the changes, a new umbrella EPUB 3.1 specification was introduced as the primary point of entry. EPUB Publication and Reading System requirements that were formerly defined in [Publications301] were moved to this new top-level specification, as was the section on Publication Resources. These changes were intended to remove confusion that EPUB Publications are equivalent to the Package Document. All common terminology was collected into this top-level specification, as well, to provide a common point of reference. An index of key concepts and terms was also added to aid navigation of the various sub-specifications.

[Publications301] was renamed to EPUB Packages 3.1 to better reflect that it defines Renditions of content through the Package Document. The EPUB Navigation Document definition was moved from [ContentDocs301] to this specification as it is a central component of a Package and not a feature to be implemented in random EPUB Content Documents. All property definitions previously defined within this specification were moved out to the [PackageVocab].

[MediaOverlays31] also saw its embedded property definitions removed to a separate vocabulary, but was otherwise unchanged structurally.

[ContentDocs31] underwent mostly cosmetic changes outside of the removal of the EPUB Navigation Document definition. Some sections were renamed to better reflect that they are not unique document types but ways of enhancing content documents (e.g., the section "Scripted Content Documents" was changed to "Scripting"), but otherwise the arrangement of sections remains largely unchanged.

[OCF31] similarly underwent some minor editorial and structure cleanup, but no sections were added or removed.

note

To comment on this change, please see Issue #640.

  3 EPUB 3.1

  3.1 New Core Media Types

EPUB 3.1 adds the WOFF 2.0 and application/font-sfnt font formats as Core Media Types.

  3.2 Clarification of Foreign Resource Fallbacks

EPUB 3.1 adds an additional clarification that foreign resources do not require fallbacks if they are not in the spine and not embedded in EPUB Content Documents.

This change will allow authors to include data files for use by scripts without unnecessary fallbacks, among other benefits.

note

To comment on this change, please see Issue #592.

  3.3 Removed support for EPUBCFI for linking

EPUB 3.1 drops the requirement for Reading Systems to support EPUB Canonical Fragment Identifiers [EPUBCFI] for hyperlinking (cf. the EPUB 3.0.1 EPUBCFI requirement).

note

To comment on this change, please see Issue #662.

  4 Packages 3.1

  4.1 Package Metadata Changes

EPUB 3.1 redefines a new minimal set of metadata in the Package Document that is intended only for use by Reading Systems in cataloguing and for display to Users. One dc:identifier and dc:title, one or more dc:language, zero or more dc:creator, one optional dc:publisher and zero or more dc:type elements are now allowed. All other DCMES elements have been removed. If authors wish to include more detailed bibliographic metadata, they are now encouraged to use the link element to attach records.

The refines attribute, previously used to chain metadata statements together, is dropped from the meta element. A file-as attribute has been added to the dc:title, dc:creator, and dc:publisher elements to handle sorting needs in Reading Systems.

EPUB 3.1 also changes the precedence order of linked records, prioritizing bibliographic information in linked records over the information included directly in the Package Document metadata element.

The OPF2 meta element has also been dropped.

note

To comment on this change, please see Issue #642.

  4.2 Removal of the NCX

EPUB 3.1 does not support the inclusion of the EPUB 2 NCX file for navigation (cf. EPUB 3.0.1 NCX). The toc attribute for referencing the file is consequently not part of the Package Document grammar.

note

To comment on this change, please see Issue #633.

  4.3 Removal of the guide Element

EPUB 3.1 drops the deprecated guide element (cf. EPUB 3.0.1 guide element).

note

To comment on this change, please see Issue #644.

  4.4 Removal of the bindings Element

EPUB 3.1 does not support the use of bindings in the Package Document to provide an alternative scripted fallback for foreign resources embedded in an object element (cf. EPUB 3.0.1 bindings).

The [HTML5] object element's intrinsic fallback mechanism (embedded content) remains for providing a Core Media Type fallback.

note

To comment on this change, please see Issue #639.

  5 Content Documents 3.1

  5.1 Addition of Support for HTML Syntax of HTML5

EPUB 3.1 adds the HTML syntax of HTM5 as a core media type. Reading Systems have to support both the HTML and XHTML syntaxes of HTML5. Authors can use either syntax for the content, and may mix documents with different syntaxes in the same publication.

A primary result of this change is that the epub:type attribute (usable only in the XHTML syntax) has been superseded by the ARIA role attribute.

The EPUB Navigation Document will require both the role and epub:type attributes be declared in order to be compatible with EPUB 3.0(.1) Reading Systems.

note

To comment on this change, please see Issue #636.

  5.2 Replacement of EPUB Style Sheets with CSS References

EPUB 3.1 removes the EPUB Style Sheets profile. In its place, more general CSS support requirements are being defined:

  • CSS support is now required for visual Reading Systems.

  • Rather than a CSS profile, EPUB 3.1 uses the “official definition” of CSS from the CSS Working Group Snapshot.

  • The restriction on the use of position: fixed is removed.

  • The restriction on the use of position: absolute is removed.

  • All -epub- prefixed properties from CSS Speech are removed due to lack of implementations.

  • The -epub-ruby-position property is removed.

  • The -epub-text-combine-horizontal property is removed.

  • The -epub-fullsize-kana property is removed.

  • The -epub-text-emphasis shorthand property is removed.

  • The use-glyph-orientation and sideways-left values of -epub-text-orientation are removed.

note

To comment on this change, please see Issue #659.

  5.3 Scripting Support Clarifications

EPUB 3.1 makes the following changes to scripting support:

  • Container-constrained scripting is limited to the [HTML5] iframe element (removed embed and object).

  • Reading Systems should support container-constrained scripting (down from "must" because of security and privacy concerns around scripting)

  • Reading Systems should support spine-level scripting in fixed layout documents and the "scrolled-doc" and "scrolled-continuous" interfaces defined by the rendition:flow property

  • If a Reading System supports spine-level scripting in reflowable documents, it must support the "scrolled-doc" interface and should support the "scrolled-continuous" interface.

note

To comment on this change, please see Issue #660.

  5.4 Addition of WCAG Support

Previously, only Scripted Content Documents were recommended to conform to WCAG. EPUB 3.1 now recommends that all HTML Content Documents conform to WCAG 2.0 Level AA. The recommendation for SVG Content Documents to conform to the SVG Accessibility Note has been updated to reference WCAG.

note

To comment on this change, please see Issue 658.

  5.5 Removal of the switch Element

EPUB 3.1 does not support the inclusion of the switch element for conditional display of content (cf. EPUB 3.0.1 switch element).

Authors are instead directed to the existing guidance on the use of the MathML alttext and altimg attributes.

note

To comment on this change, please see Issue #637.

  5.6 Removal of the trigger Element

EPUB 3.1 does not support the inclusion of the trigger element for declarative control of audio and video content (cf. EPUB 3.0.1 trigger element).

Authors are advised to use the native controls provided by the [HTML5] audio and video elements.

note

To comment on this change, please see Issue #638.

  Acknowledgements and Contributors

This section is informative

EPUB has been developed by the International Digital Publishing Forum in a cooperative effort, bringing together publishers, vendors, software developers, and experts in the relevant standards.

The EPUB 3.1 specifications were prepared by the International Digital Publishing Forum’s EPUB Maintenance Working Group, operating under a charter approved by the membership in July 2015, under the leadership of:

Active members of the working group included:

IDPF Members

Invited Experts/Observers

For more detailed acknowledgements and information about contributors to each version of EPUB, refer to Acknowledgements and Contributors [EPUB3Overview].

  References

Normative References

[ContentDocs30] EPUB Content Documents 3.0 .

[ContentDocs301] EPUB Content Documents 3.0.1 .

[ContentDocs31] EPUB Content Documents 3.1 .

[EPUB31] EPUB 3.1 .

[MediaOverlays30] EPUB Media Overlays 3.0 .

[MediaOverlays301] EPUB Media Overlays 3.0.1 .

[MediaOverlays31] EPUB Media Overlays 3.1 .

[Publications30] EPUB Publications 3.0 .

[Publications301] EPUB Publications 3.0.1 .

Informative References

[EPUB3Overview] EPUB 3.1 Overview . Garth Conboy, et al.